Hermaphroditic couplers for fiber optic cable must incorporate features that allow the coupler to perform as either a female or male plug such that identical connectors may be coupled to each other. Known hermaphroditic couplers utilize either a conventional threaded configuration wherein a coupling nut moves to a rearward or forward position or a bayonet configuration. The drawback to the threaded connection is that the coupling nut must be rotated through a number of turns to mate with the opposing connector.
Bayonet type connectors are known that use a pin or pins extending inward from a fixed coupling nut. The pins engage J-shaped grooves, one in the first connector body, the second in the mating connector body. The pins engage and slide through the long leg of the J-shaped groove then through the crook of the J and into the short leg or locking recess of the J-shaped groove to prevent the coupling nut from inadvertently loosening. In the case of a plug connecting to a plug, there may be four pins, two of which engage each of the connectors to provide a secure connection. In the case of a panel mounted receptacle, which does not include a coupling nut, there are only two pins, only one of which engages the receptacle.
There are two drawbacks to conventional bayonet connectors, the first being the movement of the connector faces as the pins move into the locking recess or short leg of the J-shaped groove. Typically the connector faces mate tightly together at the point where the pins are at the endmost tip of the crook of the J-shaped grooves. As the pins move through the crook and into the locking recess, the mating faces tend to move apart. Thus, the depth of the short leg of the J-shaped groove translates into a space between connector faces that may allow angular movement of the connectors relative to each other.
The second drawback of conventional bayonet type connectors is that when the plug is mated into a panel mounted receptacle, only one of the bayonet pins engages the receptacle. In this configuration, only one side of the plug is secured. A normal force applied to the plug may result in angular movement of the plug relative to the receptacle. In the case of fiber optic cables, such movement can result in the terminal ends of the cables being displaced from each other, interfering with or cutting off the transmission carried by the cable.
The magnitude of these problems is increased in the case of single mode cables. Multi-mode cables have a core with a nominal diameter from about 50 to 100 microns, typically on the order of 62.5 microns. Alternatively, single mode cables have a core with a nominal diameter of 8-10 microns, typically on the order of 9 microns. Single mode cables are capable of greater transmission speed over longer distances with less signal attenuation; however, because of the small core diameter, alignment of single mode cores with a connector is more critical than in the case of a multi-mode fiber. Alignment of the fibers becomes even more of an issue in the case of multiple channel single mode cables where multiple fiber optic connections must be aligned with a high degree of precision.